A I will preface my answer by saying I do primarily drainless abdominoplasties. With that being said I think both techniques are very effective and as others have mentioned you should choose the surgeon you trust and get consistent results. The complication profile between the two techniques when done correctly is very similar, specifically the risk of seroma formation. Some studies actually showed a decreased risk of seroma with the drainless.
Some patients just have a significant aversion to drains for a multitude of reasons; pain, squeamish about bodily fluids, anxiety about drain removal, the headache of recording drain outputs, restrictions on showering after surgery, etc. For these patients the drainless technique will provide great benefit.
I strongly disagree that you "cannot pull as tight" with the drainless technique. The progressive tension sutures that make the drainless technique possible actually offloads tension on the incision allowing you to pull the flap very tight.
I will be the first to admit that there are tradeoffs with the drainless technique. Most notably, increased operative time to place the progressive tension sutures (usually 15-30min). There can also be temporary dimpling of the skin in areas of the progressive tension sutures but this goes away within a few weeks. There are also rare circumstances during surgery that I may feel inclined to leave a single drain for a few days but this is uncommon.
You should go with your gut and choose the surgeon you are most comfortable with. Best of luck with your decision!